Butkus V, Klimasauskas S, Kersulyte D, Vaitkevicius D, Lebionka A, Janulaitis A. Investigation of restriction-modification enzymes from M. varians RFL19 with a new type of specificity toward modification of substrate.
Nucleic Acids Res 1985;
13:5727-46. [PMID:
2994011 PMCID:
PMC321908 DOI:
10.1093/nar/13.16.5727]
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Abstract
The characterization of MvaI restriction-modification enzymes, isolated from Micrococcus varians RFL19, is reported. Both enzymes recognize the 5'CC decreases (A/T)GG nucleotide sequence. The endonuclease cleaves the sequence at the position indicated by the arrow, whereas the methylase modifies the internal cytosine, yielding N4-methylcytosine. This type of modification protects the substrate from R.MvaI cleavage. 5-Methylcytosine in the same position of the recognition sequence does not protect the substrate from R.MvaI cleavage. R.MvaI proved to be the first example of a restriction endonuclease differentiating the position of the methyl group in the heterocyclic ring of cytosine, located in the same site of the recognition sequence. M.MvaI modifies DNA dcm+ in vitro yielding N4,5-dimethylcytosine. N4-methylcytosine cannot be differentiated from cytosine using the Maxam-Gilbert DNA sequencing procedure.
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